Radioreceiver



Patented v June 7, 1932 T-FEDF 'iS A' E'S E'ARL w. DAviDsoN, or TERRE "Hirin-rrui'nsxrmmNiA E nsnronncnlvn'n. I

' t 'Aiiipiiciation filed 'Ja nuary 12, i928. Serial no. 246,160.

This invention relates to radio-receiving apparatus or circuits, andhas for its principal'objectsthe-production of a receiving set of great sensitivity and, therefore, capable of obtaining a great distance with a-minimum number of tubes and also adapted to eliminate the usual disturbing factors interfering with clear, uniform reception. To these ends I prefer to employ an extra electron tube in the: radiofreq'uency circuit to connect one side of the coupled inductance to the grids of both tubes, but to connect the plates of the tubes differently, one plate being connected preferably directly to the aerial and the other through a coil of low distributed capacity to the other side of said inductance. I also prefer to place between said coil and the audio frequency output a crystal rectifier for eliminating disturbances and purifying the 29 tone. As an aerial I also prefer to employ a novel'type of buried antenna. This consists of a honey comb coil impregnated with paraflin or the like and buried in the ground.

Referring to the drawing in which one preferred embodiment of the invention is shown Fig. 1 is a diagram showing the circuit arrangement I may employ.

Fig. 2 is an elevation of my preferred form of underground antenna.

Fig. 3 is a similar view of the preferred form of. aerial for my circuit.

Fig. 4: is a sectional View on an enlarged scale of the central insulator used in Fig. 3.

In Fig. 1, 1 represents any form of antenna, 2 the usual variable condenser, 3 a loose coupler or coupled-inductance, the primary 4 thereof being connected to condenser 2 and to the ground G. Preferably I place a high resistance say one megohm around 0 said condenser 2. My two detector tubes are shown at 6 and 7, and the circuit is of the re generative or feed back type. Preferably I connect the grids 8 and 9 of both tubes to one part (preferably the primary 4) of the coupler through a grid leak 22 and grid con.- denser 23, while the plate 10 of tube 7 is connected to a mid-part or tap in a self-inductance coil 11. Said coil is preferably of low r0 distributed capacity for which the honey 0 comb type is suitable. The secondary 4: of

the coupler 3 is also connected to thefirsttur'n of said coilll, whilethe'last'turn of said coil is carried to the ground through variable resistance 12 and also to the output represented diagrammatically at 15, it being un derstood that I can employ any ype offaudio frequency"amplification'if desired."

; The plate 10' of tube =6"I"'con nect'to the aerial as shown. =Th'e filaments or electron discharge devices are lighted infth'e usual manner froin-A battery '13 and onejside thereof is also connected back t o'the primary 4 of, coupler 18 for regenerative actiong The secondary 4" of'th'e c0upler1'is connect'ed through variable resistance l l to one'side (if the output 15, the other'side of'theyoutput being connected in the usual manner tothe B battery 16 "and t'oA battery 131 also preferto place'a crystal 17, which maybe similarto'the usual crystal rectifier ordetector and which is preferably of the pressure type, such as iron pyrites, in the circuit in such a manner as to feed a small amount 'of audio frequency current to thecrystal where it is met by the radio-frequency current, thus making a 'very' sensitive circuit as well as making more volume of'sound. To this end the crystal is'shown as placed between the aforesaid coil ll oand the output 15, with the direct connection. from secondary 4 shunted the'rearoundf through resistance 14: placed toward the "audio frequency side." This has been foundtb'y actual trial to' have a very beneficialaction 'in'i'cutting out static and increasing the selectivity (both primary and secondary) and in combination with the honey comb coil 11 and special type of aerial described below gives a reception fwhich ,is clear even under the most advei'se conditions, such as caused by the 'northern'li'ghts -or "an approaching storm without the" sacrific'ef of distance. i

Regarding the increased sensitivity which I' am able to obtain bymy invention, I have as'yet formed no theory but it may be by reason of inter-regenerative action between the-tubes. I

' Asstated hereinbefore, my preferred'typ'e of aerial for my circuit is aburied inductance coil 20 (Fig. 2). This coil is preferabl-y of the compact high inductance, low-distributed capacity type such as the honey comb or lattice work coil. Preferably I completely enclose the coil in paraflin 21 or other moistureproof insulating material and bring both ends to the surface of the ground, either end being connected to my receivingcircuit.

In and 4 Ishow another excellent form of aerial for use in my circuit. This antenna is made in the form of an X,'with wires 25 and 26 joinedat the top by Wire??- and crossed through separated holes 28 and 29 in an insulator 30. It is shown as supported at the top by A? frame 31 and insulators 33, 33 and 34 and at the bottom by a" similar. frame. 35 andinsulators, and is normally, supported vertically on brackets- 36.

In accordance with the provisions of the patent statutes, I: have herein described the principle and operation. ofmy invention, together' with the apparatus which I now consider to represent the best embodiment thereof, butI desire to haveit understood, that the apparatus shown isonly illustrative. and that the invention can be carried out-by other means. Also,,whileit.is designedtdusethe various features and: elements in: the combination aildrelations described, some offthese may be. altered and. others omitted. without interfering With the more general results outlined, andgthe invention extends to such use, Having. described my invention, what I claim andv desire to secure byLettersB ab entisz. 1

. 1. A radio receiving circuit comprising the combination with; anaerial, a: coupler, and an inductance, of aplurality of electron tubes having-the grids-thereof connectedto one side of thecouplenthe plate of. one tube. connected tothe aerial and: the plate of the other tube connected to a tapin saidindhctance, .saidrinductance beingconnected. at one end to the secondary, of. said coupler and. at the other endto the ground. and to theoutput.

. 2.. A; radio receiving circuit comprising. the combination with an aerial, a coupler, and an inductance, of a plurality of electrontubes having the grids; thereof connected to one side of. the coupler,.the. plate of'one tubeconnected. to the aerial and the platerof theother tube connectedto a tap in said inductance, said inductancebeingconnected at one..end to theysecondary of said; coupler. and at. the othenend. to the ground and. to the output,

- 2 and. a crystalalso in circuit between said inductance and they output.

3. A radio receiving circuit comprising the combination with a honey comb coil aerial buried in. the. ground, a coupler, and an inductance, .of a' plurality of electron. tubeshaving the grids thereofconnectedto-one side. ofthe coupler, the plate of one tube connected to theaerialand the-plate ofthe-other-tube connecteid-to amap'in said inductanee, said inductance': being. connected. at; one: endto .the sec-- inductance, said inductance being connected r at one end to the secondary and at the other end to the output.

5. Ina. radio receiving circuit, the combination withtheaerial, a plurality of thermionic tubes having, the grids thereof. connected. to the input, atapped selfsinductance coil connected at. a midpoint to the. plate of one-tube, a coupler connected to one end of said coil, an output circuit connected to said coupler, anda crystal-connectedbetween the otherend of said. coil and the output.

. In testimony whereof]; have aflixed my signature EARL VVL DAVIDSON.

of said coupler ground and to the 

